Cost estimate for renovating a 1970s semi-detached house according to KfW or BAFA

Why photovoltaic, is that mandatory?

Only from 2026 with roof renovation. In 2025 it would not yet be mandatory - but if the budget allows and you already have scaffolding on the roof, you should consider it.

Only from 2026 onwards for roof renovation. In 2025 it would not yet be mandatory - but if the budget allows and you are already on the roof with scaffolding, you should consider it.

But for example, first do without an attic, that can also be retrofitted...

Good evening everyone,
thanks again for the numerous feedbacks. I find it difficult to address each one individually, but I will try to summarize.

To achieve KfW55 or 70 EE, all the measures mentioned (according to the building surveyor) would probably be necessary, and the costs estimated by him fit (except for the ventilation and photovoltaic system), provided everything is done by professional companies. Did I understand you correctly?

If I distance myself from the original wish for a KfW 55/70EE house, then I see the following measures that need to be done and that I also want to do:

[*
Roof renovation is necessary, and for the photovoltaic system I would like to have it installed for the reasons you mentioned.
[LIST=1]
[*]What actually fits on a roof area of 95 sqm? I have not deducted roof windows now, I will attach pictures, and those should of course also be renewed. The roof truss is intact. ( you are right. With "insulation of top floor ceiling" I formulated it poorly or incorrectly.
[*](optional) What additional costs should I expect if I consider adding a dormer about 4 m wide on one side during the roof renovation? Total roof width 7.24 m


[*]Windows/front door
[*]Underfloor heating + new water pipes to be implemented with the relatively new heating system from 2018. Heat pump is not a must but the preparations would be considered if a heat pump is to be operated at some point.
[*]New bathrooms + guest WC
[*]Electrical work
[*]Painting work (house painting and inside Q3 with painter’s fleece)
[*]New floor coverings
[*]Terrace (does not have to be done immediately)
[*]Front garden (does not have to be done immediately)

- For the roof renovation I will have to get offers. According to the current cost estimate (without dormer) with photovoltaic system about 75,000 EUR, correct?
- Windows/front door significantly cheaper according to friends circle in Poland and with the same quality. I would not google suppliers but rather rely on contacts from the friends circle; 20,000 EUR?
- Underfloor heating, new water pipes, and new bathrooms/guest WC: I may save the most here because my best friend will do the work. He is in the heating, bathroom, and sanitary master business. Material costs are clear, but for the labor costs he does not want to make money from me (of course I will pay him)
- Electrical work through specialist company; 20,000 EUR
- Painting work, floor coverings in EL

Do you think I am too naive with about 200,000 EUR +/- for the above measures? (I leave subsidies aside)

And if we buy the house, I expect about 1 year until it is ready for us to move in. Do you think this is realistic?
We would rather not move in with 3 children (14 y, 4 y and 1 y) during the construction site. We will accept the double burden for that period.

I still don't see the roof as that expensive. We paid about €350/sqm for everything at 165sqm, which would be around €35K for you. Plus possibly a regional surcharge, but certainly not almost double. Photovoltaics: Is the roof oriented East/West or North/South? With East/West both sides would make full sense, with North/South only one --> has a strong impact on costs.

From purchase to move-in ready in 1 year is unrealistic. Better count on 1.5 to 2 years. The transfer of ownership alone can take 2 months, and especially electricians and roofers are notoriously fully booked.

The transfer of ownership alone can sometimes take 2 months

What does that have to do with the renovation? The purchase price is paid, the keys are handed over, and the transfer of ownership in the land register follows at some point – it doesn't matter when.

You are right, but it can also take time until the handover of the keys. Our example: June 1st, purchase contract signed, August 4th, key handover. In between, waited 6 weeks for the [Vorkaufsrechts-Verzichtserklärung] from the city. Construction start was, by the way, in January, although we began gathering offers directly in August.

We also see this with friends, a sample of 4 renovations, none of them managed to complete it within a year. It may be possible, but I wouldn’t rely on it.